The X-ray generation efficiency of transmission X-ray generators that irradiate a transmission target with electrons to generate X-rays is generally extremely low. When accelerating electrons to high energy and irradiating the target to generate X-rays, only about 1% or less of the energy of the colliding electrons becomes X-rays, and the remaining about 99% or more becomes heat. Thus, an increase in X-ray generation efficiency is required. When electrons collide with the target, reflected electrons are generated. It is known that the reflected electrons do not contribute to generation of X-rays for use.
PTL 1 discloses an X-ray tube whose X-ray generation efficiency is increased by disposing an anode member having a conical channel whose opening diameter is decreased from an electron source toward a target between the electron source and the target and by elastically scattering the electrons on the channel surface to let the electrons incident on the target.
PTL 2 discloses a transmissive X-ray target in which target metal is formed on a ceramic or glass X-ray transmission window substrate.